Highways and surface streets are replete with signs providing a variety of information. Such information may include street/exit names, distance/instructions to destinations, traffic condition notices, traffic safety rules (including speed limits, lane changing, etc.), as well as possible advertising or other information.
Some traffic signs use active display signs, for example, to warn of traffic congestion, construction and accidents ahead on the highway, whereas the displayed information may be actively changed and/or updated. The information displayed may be pre-programmed and displayed without any feedback as to whether there are vehicles on the road with drivers to see and benefit from the information. This may result in needless power consumption. Furthermore, such signs often project the message with a Lambertian or other large solid angle illumination pattern that includes unnecessary projection to the road sides or vertically, where there is no need, since there are no viewing drivers or passengers in these directions to benefit from the information. Additional power may be wasted in such non-discriminating light projection.
There is a need, therefore, for active signage capable of projecting dynamically changeable information directed at approaching vehicles only when they are sensed.